Fabric coating



MarchZS, 1941. J FORD ET AL 2,235,872

FABRIC COATING Filed June 16, 1939 2/ /9 15 m H J i w H i1 aiented Mar. 25, ,1941

UNITED STATES FABRIC COATING Jay 1'. Ford, Grand Blanc, and William s. Kirk,

Flint, Mich, assignors to General Motors Corporation, Detroit, Mich., a corporation of Dela- Application June 16, 1939, Serial No. 279,430

a 2 Claims.

This invention relatesto fabric coatings and particularly to the coating of fabric which is to be used for making fuel pump diaphragms. Reference is made to our prior applications,

5 Serial No. 190,272, for Fabric coating, filed February 12,1938, and Serial No. 238,950, for Fabric coating, filed November 5, 1938. This application is a continuation in part and includes matterdivided out from our earlier filed applicapp tions.

he with the invention of our prior applications it is an object of this invention to so coat diaphragms that they may be and remain flexible for long periodsof time and throughout a great it range of tperature; and that the coating shall not appreciably dissolve in gasoline or in orgarlic solvents found associated with gasoline. its a further object the coating should resist clause which may be occasioned by metricto tional resistance between the adjacent layers of a laminated diaphragm.

The accompanying drawing shows a sectional view of a conventional fuel pump in its single ile. as in the drawing i represents the body of the pump and it a cover therefor. at i is shown a laminated diaphragm positioned between upper disc it and lower disc l. The diaphragm is adapted to be reclprocated by an engine operau ated lever t, the end onlyof which is shown in the thawing. The lever t pulls the diaphragm through the instrumentality of a rod ll secured to the diaphragm by attaching means it. The discharge movement of the diaphragm is made at by spring it. The fuel enters the pump chamher through a passage 19 and is delivered through a passage 2i and through an outlet 23. The outlet valve 26 only is shown, its spring being marked it. to We have foundthat alkyd resins afford the answer to the obectives recited above. These resins are formed as the reaction products of polyhasic acids with polyhydric alcohols, preferably alcohols having at least three hydroxyl id groups. f the polybasic acids we prefer to use one having at least two carboxyl groups separated by live or more CH2 groups forming a long straight chain, such an acid as sebacic acid, and it is this acid which is believed to be i l most useful in producing a resin having the desired flexibility and the high degree of nonsolubility in organic solvents. We prefer to use glyc'erlne forthe alcohol. j

a. diaphragm coated as above does not posit sees quite the freedom from solubility that may be desired. We therefore use another polybasic acid together with the sebacic acid in making the resin. Numerous other acids may be associated with the sebacic acid. Uf these others We prefer to use one or more of the polybasic acids having no more than three carbon atoms between the carbonyl groups. Typical of such acids are citric acid, which is now preferred, and tartaric acid. We are aware that when tartaric acid or citric acid is used certain inter- 1 mediate acids may be produced when the miin ture is heated, such 'as malic acid, methyl succinic acid in the case of tartaric-acid and aconitic acid in the case of citric acid. These intermediate products might be obtained commercially and used directly with the sebacic acid. We have found that citric acid when used with sebacic acid and glycerine renders the resin less soluble in organic solvents and is therefore highly desirable when the fabric is to be. used for fuel pump diaphragms. A

it is quite common in the use of coated fabric for fuel pumps to use a plurality of laminations. Perhaps as the result of friction between the layers there has occurred a slight song off of 5 the coating and a consequent development of porosity. To avoid this defect we have found it desirable to add what may be termed a filler. The hller apparently lessens the swelling and softening of the coating and prevents its being 30 scuffed on. For the filler there may be used forms of carbon such as amorphous carbon, lamp blaclr, charcoal or graphite. it has also been found that there may be used powdered aluminum or oxides of iron, copper or manganese. it is also possible to use starches, cornstarch andarrow root having been considered. At present we regard lamp black most favorably as a filler. It will be understood that the use of the filler to prevent song of the coat- 40 ing is in addition to its utility in preventing solubility of the coating in the fuel as set forth in the parent case where it was proposed to use the filler in place of the second resin. In the present case it is used together with a second resin and serves'the double purpose described. Moreover, improvement in insolubility of the coating resulting from the addition. of lampblack' is a characteristic quite apart from and in addition to its utility for preventing the scuffing off of the coating. It has been found that lamp black should be used to the extent of at least 5% by weight. Below 5% the efficiency is not satisfactory. The quantity may be increased up to 20%, but above "20% it is found diificult to keep the lamp black in suspension in the liquid resin. It has been determined therefore that 5% and 20% are the limits within which the lamp black should be used.

The inventive idea is therefore the coating of fabric with an alkyd resin made from the reaction of a polyhydric alcohol such as glycerine together with a long chain polybasic acid such as sebacic acid to secure pliability, and a second acid such as citric acid to secure maximum insolubility and a filler such as lamp black to prevent the scufllng off of the coating and to aid in preventing solubility.

It should be explained that there are many other uses for this invention than its use with fuel pumps. Utility will be found wherever such a coated fabric is to be used in contact with liquid media and especially where the media may contain organic solvents. It is believed the possibility of using diaphragms coated as herein disclosed may lead to the use of such flexible diaphragms in many applications where in the past their use has been thought to be impractical. For this reason it will be understood that although the immediate occasion for the invention is the making of a more serviceable fuel pump, the invention is by no means limited to that one field of usefulness.

We claim:

1. A flexible fabric imperviously coated with a resinous product of polyhydric alcohol with sebacic acid and citric acid, together with between 5% and 20% by weight of lamp black to prevent solubility and scuffing off of the coating.

2. A flexible fabric for fuel pump diaphragms imperviously coated with alkyd resins constituting the reaction products of polyhydric alcohol with sebacic acid and citric acid, the sebacic resin affording a relatively greater pliability but a lesser solubility in organic solvents and the citric resin affording a relatively greater insolubility but a lesser pliability, together with between 5% and 20% by weight of lamp black to prevent solubility and scuffing off of the coating.

JAY T. FORD. WILLIAM S. KIRK. 

